Annotated record of the detailed examination of Mn deposits recovered by the Geological Survey of Japan (GSJ) during the 1971-1974 period in the Pacific Ocean

In 1974, the Geological Survey of Japan began its systematic investigation of manganese nodules in the Central Pacific Basin on the new geological research vessel Hakurei Maru. The first cruise (GH 74-5) was carried out over an eastern part area of the Basin (6°-10°30'N, 164°30'-171°30'W), and the authors report here the preliminary results on the occurrence of manganese nodule deposits, paying particular consideration to their relationship to submarine topography and surficial and sub-bottom sedimentary facies. The surveyed area comprises a deep-sea basin at 5,000-5,400 m, defined to the north and east by the chain of seamounts and guyots of the Christmas Ridge. The deep-sea basin is divided roughly into 2 contrasting topographic features. The eastern part is characterised by flattened topography resulting from continuous deposition of turbidities; the meridian and western parts are characterised by gently rolling topography and the existence of a large number of deep-sea hills. Manganese nodules are almost lacking in the former flattened eastern area, whereas they are widely distributed in the latter rolling meridian and western parts. The population density of nodules varies from less than 1 Kg/m² to 26 kg/m² and the higher density is found in the siliceous-calcareous ooze zone of rather small, flat basins surrounded by deep-sea hills. The density is closely related to the thickness of the transparent layer obtained by 3.5 kHz PDR profiling over the whole area. Considering the various data of grab sampling, 3.5 kHz PDR profiling and to a lesser extent of deep-sea television and camera observations, the most promising manganese field in the present area seems to be confined to the north of the western sector of the area.

Geological map of Potter Peninsula (King George Island, South Shetland Islands, Antarctic Peninsula)

We present here a new geological map of Potter Peninsula (King George Island, South Shetland Islands). Like on adjacent Barton Peninsula, the morphology on Potter Peninsula is predominantly characterized by a glacial landscape with abrasion platforms offshore, in parts steep cliffs along the coast, and a rather smooth, hilly countryside in the interior. Potter Peninsula forms part of the downthrown Warszawa Block. The volcanic sequence cropping out here belongs to the King George Island Supergroup, with an observed local minimum thickness of approx. 90 m (Kraus 2005). The most prominent morphological feature is Three Brothers Hill (196 m), a well known andesitic plug showing conspicuous columnar jointing. It marks the final stage of activity of a Paleogene volcano, whose eruption products (lava flows and pyroclastic rocks), together with hypabyssal intrusions related to the volcanism, make up most of the lithology observed on Potter Peninsula (Kraus 2005). The Three Brothers Hill volcanic complex is eroded down to its deepest levels. Thus, the stratigraphically deepest units from the initial phase of volcanic activity are cropping out in some parts (Kraus & del Valle, in Wienke et al. 2008). The lithology on Potter Peninsula comprises lava flows (~50%), pyroclastic rocks (ash-fallout, pyroclastic flow deposits, volcanic breccia and agglomerates, ~30%) and hypabyssal intrusions (dykes, sills and small subvolcanic intrusive bodies, ~20%). 40Ar/39Ar datings carried out on magmatic dykes from Potter Peninsula indicate a short, but intense intrusive event during the Lutetian (Kraus et al. 2007).

Geological reference standards (JLK-1,JSD-1, JSD-2, JSD-3,JMS-1, JMS-2) measured by Itrax-XRF core scanner in different exposure times

X-ray fluorescence (XRF) core-scanning is a fast and nondestructive technique to assess elemental variations of unprocessed sediments. However, although the exposure time of XRF-scanning directly affects the scanning counts and total measurement time, only a few studies have considered the influence of exposure time during the scan. How to select an optimal exposure time to achieve reliable results and reduce the total measurement time is an important issue. To address this question, six geological reference materials from the Geological Survey of Japan (JLK-1, JMS-1, JMS-2, JSD-1, JSD-2, and JSD-3) were scanned by the Itrax-XRF core scanner using the Mo- and the Cr-tube with different exposure times to allow a comparison of scanning counts with absolute concentrations. The regression lines and correlation coefficients of elements that are generally used in paleoenvironmental studies were examined for the different exposure times and X-ray tubes. The results show that for those elements with relatively high concentrations or high detectability, the correlation coefficients are higher than 0.90 for all exposure times. In contrast, for the low detectability or low concentration elements, the correlation coefficients are relatively low, and improve little with increased exposure time. Therefore, we suggest that the influence of different exposure times is insignificant for the accuracy of the measurements. Thus, caution must be taken when interpreting the results of elements with low detectability, even when the exposure times are long and scanning counts are reasonably high.

Major elements and trace ferrides in deep sea cores obtained during the Swedish Deep-Sea Expedition in 1947-1948

Samples from sediment cores collected during the Swedish Deep-Sea Expedition 1947-1948 have been analyzed in the Geochemical laboratory of the Geological Survey of Sweden. Most samples were placed at our disposal by Professor Hans Pettersson, leader of the expedition mentioned. For complementary studies, samples from the Atlantic and Indian oceans were included in our investigation and the samples placed at our disposal by Professor B. Kullenberg, Göteborg. From the Tyrrhenian Sea we got samples from Professor E. Norin, Uppsala.